1. Field of the invention
This invention relates to a three dimensional display system and, more specifically, to a system capable of displaying images in three dimensions which are projected onto a screen in two dimensions.
2. Brief Description of the Prior Art
It has been known in the prior art to modulate or scan a beam, such as a laser beam and then to project the scanned beam onto a screen. Examples of such systems are set forth in Baker U.S. Pat. Nos. 3,471,641 and 3,549,800.
It has also been long desired to provide a three dimensional display. Prior art systems for creating such a display have involved moving a flat plate mirror or flexing a plastic mirror to reflect a CRT image to create a volume display. Similar techniques have employed a Mylar membrane stretched over a metal ring and silvered on the front surface, such mirror being vibrated to reflect the information displayed on the CRT in synchronism with the mirror motion. Such techniques and techniques for converting a cathode ray tube two dimensional display into a three dimensional image are discussed in the article "Terminal Puts 3-Dimensional Graphics on Solid Ground", by Harry S. Stover, Electronics, July 28, 1981.
Prior art three dimensional display techniques were limited because of their use with CRT screens in that the produced image may be viewed only from selected angles. Moreover, such prior art systems have generally not been able to produce real time images and have been limited in the possible vibration frequencies of the screens. Moreover, the use of vibrating mirrors has created difficulties due to the relatively large mass of the mirrors which prevent substantial deflections. For example, such prior art systems have generally been capable of providing a mirror displacement of about 0.4 millimeters.
A need thus arose for a simple and economical three dimensional display system that could produce substantial displacement at a variety of frequencies in order to provide three dimensional images which can be viewed from all angles. U.S. Pat. Nos. 1,794,103, 3,682,553 and 3,970,361 set forth typical prior art displays of the above noted type. Such prior art systems were generally limited as to the size of the imaqe displayed and is affected by G forces, thereby presenting problems in environments where G forces exist, such as in aircraft.
The above noted problems of the prior art were minimized and there was provided a three dimensional display system which was not substantially affected by G forces and wherein the size of the displayed image and screen is determined by the size of a disk and motor. This system is set forth in the above cited related application of Felix Garcia, Ser. No. 231,638, filed Aug. 8, 1988. The system in accordance with the invention in that application can be used, for example, in business and industry uses, such as solid animation, radar display, molecular research, resonant frequency and harmonics display, military, computer graphics, and the like.
The system in accordance with a first embodiment thereof includes a disk-like screen connected to the end of a motor shaft. The disk is attached to the shaft of a motor at a 45 degree angle, although this angle can be varied to provide a larger or smaller height or z-axis dimension, so that, as the disk rotates, a displacement of any given point thereon along the z axis takes place. The image is formed on the screen by projecting a light beam, such as from a laser, through a modulator and toward a scanner which produces an x-y scan of the beam on a screen, the screen therein being the disk discussed hereinabove. The disk can be translucent, such as lucite, so that images can be projected thereon onto the front and/or rear surfaces thereof. The modulation or strobing of the scan is then synchronized with the rotating disk by control of the motor speed so that a three dimensional pattern appears on the screen. It can be seen that any point on the x-y scan from the scanner which impinges upon the screen will move along a z-axis direction since the screen or disk at that point produces such z-axis movement. This movement of the displayed image provides the three dimensional effect. The adjustment of the angle between the disk surface and the x-y plane of the scanned x-y image will determine the z-dimension or height of the three dimensional image, the disk angle being adjustable on-line, if so desired.
While the disk therein is a planar opaque screen for receiving a scanned image thereon on one surface thereof, the screen can take many other forms. For example, the disk can be translucent, such as lucite, and thereby capable of receiving a scanned image thereon on both major surfaces. The lucite disk can be in the form of a pair of angularly truncated cylinders with the same which fit together at the angularly truncated surfaces to form a new cylinder wherein the surfaces at which truncation takes place are translucent. In addition, the screen can take on shapes other than planar, it merely being necessary that at least some portion thereof move in the z-direction during rotation thereof while projection of the x-y image thereon takes place to provide the three dimensional image. As a further embodiment, the disk can be placed in a gas-filled CRT with the image impinging thereon being the scanned beam of the tube. Phosphors can be disposed on the disk which, when excited, will form the three dimensional image. As a still further embodiment, the screen can be planar and disposed normal to the projected x-y image. The three dimensional affect is then provided by moving the entire screen along the z-axis in synchronism with the scanned x-y image to provide the three dimensional affect. A cam driven shaft attached to the screen can provide such screen movement along the z-axis.
While the above described prior art provides a surprisingly realistic real time three dimensional display, it is readily apparent that two conical areas extending upwardly and downwardly from the axis of rotation of the screen are incapable of receiving a portion of the display. In addition, the display cannot appear along the center point of rotation since the display does not move along the axis at this point. A still further problem is that of altering the angle of the disk easily or on-line to alter the volume traversed by the disk during rotation to control the volume displaced by the display. A yet further problem with the cited prior art is that an observer cannot simultaneously view the three dimensional display as well as a separate two dimensional display superimposed thereon.